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Young massive star clusters in nearby galaxies *
I. Identification and general properties of the cluster systems
S.S. Larsen 1 and
T. Richtler 2
Received 11 January 1999 / Accepted 18 February 1999
Using ground-based UBVRI CCD photometry we have been carrying out a search for young massive star clusters (YMCs) in a sample consisting of 21 nearby spiral galaxies. We find a large variety concerning the richness of the cluster systems, with some galaxies containing no YMCs at all and others hosting very large numbers of YMCs. Examples of galaxies with poor cluster systems are NGC 300 and NGC 4395, while the richest cluster systems are found in the galaxies NGC 5236 (M 83), NGC 2997 and NGC 1313. The age distributions of clusters in these galaxies show no obvious peaks, indicating that massive clusters are formed as an ongoing process rather than in bursts. This is in contrast to what is observed in starbursts and merger galaxies. The radial distributions of clusters follow the H surface brightnesses. For the galaxies in our sample there is no correlation between the morphological type and the presence of YMCs.
Key words: galaxies: photometry galaxies: spiral galaxies: star clusters
* Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and with the Danish 1.5-m telescope at ESO, La Silla, Chile.
Send offprint requests to: S.S. Larsen
Online publication: April 12, 1999